The objective of this project is understand the extent to which humans absorb, metabolize, and eliminate volatile organic compounds to which they may be exposed as a result of environmental contamination. Of special interest to us is the range of normal variation in these processes, and the factors which influence this variation. To better understand the underlying physiology, this project has as one of its central features the development and validation of a detailed mathematical mode of absorption, metabolism, and elimination processes in humans. Our past success in using this model to describe the operation of these processes for toluene, with very good accuracy, leads us to anticipate that this model will be able to describe the behavior of other solvents with different biological and chemical properties. Most important, the model relies on only a few readily measured individual characteristics (e.g. body fat composition, height, simple measurements of metabolic rate such as respiratory ventilation rate) to predict the individual's response. The results of this study will therefore support relatively accurate health risk assessments and epidemiologic studies, without requiring complex or detailed input data.